What is the recommended starting dose for tizanidine (Zanaflex)?

Recommended Starting Dose for Tizanidine

The recommended starting dose for tizanidine is 4 mg orally, which can be repeated at 6-8 hour intervals as needed, with gradual titration in 2-4 mg increments to achieve optimal effect. 1

Dosing Guidelines

Initial Dosing

• Start with 4 mg per dose
• Can be administered up to 3 times daily (every 6-8 hours)
• Maximum of three doses in 24 hours
• Total daily dose should not exceed 36 mg 1

Titration

• Increase dose gradually in 2-4 mg increments
• Titrate to optimal effect (satisfactory reduction of muscle tone at a tolerated dose)
• Allow 2-4 weeks for proper dose titration due to wide interpatient variability 2

Special Populations

Elderly Patients

• Start at lower doses (2 mg)
• Higher risk of sedative and hypotensive effects 3
• Titrate more slowly

Patients with Hepatic or Renal Impairment

• Significant dose reductions required 3
• More cautious titration recommended

Pharmacokinetics

• Peak effect occurs at approximately 1-2 hours after administration
• Effects dissipate between 3-6 hours 1
• Food has complex effects on tizanidine pharmacokinetics
  • Can result in clinically significant differences when switching between fed and fasted states
  • Consistent administration (either always with food or always without) is recommended to avoid fluctuations in drug levels 3, 1

Common Adverse Effects

• Dose-dependent sedation and drowsiness (most common)
• Dry mouth
• Dizziness
• Ataxia
• Lethargy 3

Important Considerations

Drug Interactions

• Contraindicated with CYP1A2 inhibitors 3
• Monitor for increased adverse effects when combined with other CNS depressants

Discontinuation

• Gradual tapering is strongly recommended rather than abrupt discontinuation
• Withdrawal symptoms may include:
  • Rebound tachycardia
  • Hypertension
  • Hypertonia
  • Visual and auditory hallucinations
  • Anxiety, agitation, and delirium
  • Tremors 3

Clinical Efficacy

• Effective for muscle spasticity associated with cerebral or spinal disorders
• Also used for myofascial pain, lower back pain, and other pain syndromes 4
• Studies show reduction in mean muscle tone scores of 21-37% versus 4-9% for placebo 2
• Improvement in muscle tone occurs in 60-82% of patients 2

Monitoring

• Assess for excessive sedation, especially during initial titration
• Monitor for hypotension
• Evaluate therapeutic response (reduction in muscle tone and spasticity)
• Consider liver function monitoring with long-term use

Tizanidine's dose-related adverse effects make it prudent to begin with lower doses and gradually titrate upward to find the optimal balance between efficacy and tolerability for each patient.